The Chronicle Gate vol. 1 Etheareal by N. Lang

What if you ended up on a planet. . .and had no idea how you got there?
On a planet called Ethereal live creatures known as the Elouse. A couple of kids discover a human child and take him in. While their dad, Jasper, tries to find the planet “Earth” (which doesn’t exist in their galaxy) their mom, Ellen, and her girls, Taylinn, and Avigale are left to welcome and care for, Sinya, who has no recollection how he got there in the first place. Sinya tries to fit in his surroundings and make friends but some are too afraid, including Taylinn and Avigale. Taylinn finds out her dad is going away in a secret space ship, but she over hears that the mission is really “to save his family from him?” Could he mean Sinya? Sinya starts seeing Mer-Dragons, a made-up tale told to him by Avigale and Taylinn but this Mer-Dragon talks to a being known as “Malic,” one that means danger for Jasper and the family. But no one will believe him. When Taylinn finally sees the truth of the danger for herself, she tries to alert her friends, but just like Sinya, no one will believe her, including her mother. Now in order for Sinya to get back home, these unlikely pair must team up to save Jasper, and his family from the coming danger of Mer-Dragons!